Air purifiers for wildfire smoke: who needs one and how they can help

What’s an Air Purifier and Who Needs One? Air purifiers are devices that are designed to clean indoor air by trapping harmful particles like dust, pollen, and smoke. While some people might call them "air purifiers," the proper term is actually "air cleaners" because they only filter the air and do not purify it. They are especially useful for people who have asthma, allergies, or respiratory problems and for anyone who lives in an area with bad air quality, such as in areas where wildfires have occurred. The American Lung Association's Jill Heins explains that the vast majority of air purifiers capture such pathogens as viruses but don't guarantee all germ-free environments, without such specific features like germicidal UV light. Air purifiers can become priceless to a segment of vulnerable individuals—children, pregnant persons, elderly adults, and patients of chronic illnesses. When the air quality index reaches 150 or more, experts suggest that everyone consider using one to reduce health risks from particulates like PM2.5. Air purifiers operate through a simple mechanism: a fan draws in air from the room and pushes it through filters designed to capture fine particles. The most effective of these filters are HEPA (High-Efficiency Particulate Air) filters, which trap up to 99.97% of particles as small as 0.3 microns. These filters are particularly effective against allergens like dust, pollen, and pet dander. In addition to HEPA filters, some air purifiers come equipped with carbon filters that remove odors and volatile organic compounds (VOCs) like those found in paints and cleaning products. While certain models include UV lights or ionizers, experts caution against ionizers, as they can produce ozone—an air pollutant that can be harmful to health. The size of the unit and its Clean Air Delivery Rate (CADR) are important factors to consider. Make sure the purifier you choose is adequate for the size of your space, and remember to regularly replace filters to maintain peak performance. Even if you already have an HVAC system in your home, an air purifier can still be beneficial. HVAC systems typically don’t filter out fine particles like an air purifier with a HEPA filter can. For maximum air quality, it’s recommended to have an air purifier on each floor of your home, particularly in areas where you spend the most time, like your bedroom or living room. In smaller spaces, you can get away with using just one unit, moving it from room to room as needed. While some HVAC systems come with advanced filters that may help, they generally can’t match the efficiency of a dedicated air purifier in tackling airborne pollutants, especially those that are smaller or harder to capture. If you’re concerned about air quality during wildfire season, supplement your HVAC system with an air purifier to get the most protection. An air purifier should be used whenever outdoor air quality dips, especially when the Air Quality Index (AQI) reaches levels above 100 (the orange zone). During wildfire season, this can happen regularly, so many people choose to run their air purifiers continuously to maintain healthy air indoors. While running one all day may add a small cost to your energy bill (around $60–$120 per year depending on the model), the health benefits—especially for sensitive groups—are well worth it. Some models come with built-in sensors that monitor air quality and automatically activate the purifier when particle levels rise, which can help save on energy use while ensuring your air stays clean. However, note that not all models track ozone, VOCs, or carbon dioxide, so it’s important to ensure you’re using a device suited for your specific needs. Air purifiers come in a wide price range, from budget models at around $150 to premium options reaching $1,500. For most people, a reliable air purifier for a single room can be found for under $300, and it will be more than adequate for typical wildfire or pollution-related air quality concerns. If you’re looking for a more affordable solution, the DIY Corsi-Rosenthal box—made from a box fan and HEPA filters—has been shown to be both effective and cost-efficient. With a CADR rate of 600 to 850 cubic feet per minute, this homemade purifier can compete with store-bought models for a fraction of the cost. To maintain clean indoor air, it’s important to adopt a comprehensive approach. Avoid burning things indoors—whether it’s cigarettes, candles, or cooking with natural gas—as these can all worsen air quality. If you do cook with gas, use an exhaust fan and open a window if possible. Also, opt for cleaning products free of harmful chemicals, and vacuum regularly to remove dust and pet dander. During wildfire season, it’s crucial to dust and clean more frequently since pollutants like polycyclic aromatic hydrocarbons (PAHs) can linger on surfaces. By combining an air purifier with good cleaning habits, you can significantly improve the air quality inside your home, even during wildfire outbreaks.